A judge in the United States has ordered damages awarded to Apple against Samsung be cut by 40% and a new trial held to assess the level of damages.
Last year Apple was awarded $US1 billion in the biggest damages payment in a series of global legal fights between the two companies over patents.
In his ruling the judge in California said the jury which set the original award, had incorrectly calculated part of the damages.
The companies are set to meet again in court and the $US450.5 million ordered to be removed from the payout will be reassessed and could be increased or lowered.
At the trial, Apple convinced the jury that Samsung had infringed its iPhone and iPad patents, the BBC reports.
The patents case encompassed 14 products that Apple said Samsung had used Apple patented designs in.
The jury found that some Samsung products illegally used Apple ideas such as the bounce-back feature.
The two companies have court cases in eight other countries, including Samsung's homeland South Korea, Germany, Japan, the UK and Australia.
The firms sell one in every two mobile phones between them. Last year, the South Korean company overtook Apple as the world's biggest seller of smartphones.